1. Field
The following disclosure relates to a halosilicate phosphor and a white light emitting device including the halosilicate phosphor. More particularly, one or more exemplary embodiments relate to a halosilicate phosphor having a large full width at half maximum (“FWHM”) and a white light emitting device including the halosilicate phosphor.
2. Description of the Related Art
A conventional optical system may include fluorescent lamps or incandescent lamps. Fluorescent lamps, however, cause environmental problems due to high levels of mercury (Hg) included therein. Also, conventional optical systems have very short lifetimes and/or low efficiencies and thus are unsuitable for use energy saving applications. Therefore, research is being performed to develop white light emitting devices having high efficiencies and extended lifetimes.
White light emitting devices are able to produce white light using three methods as follows. In one method, red, green and blue phosphors may be excited by an ultraviolet light emitting diode (“UV LED”) acting as a light source to produce the white light. In another method, red and green phosphors may be excited by a blue light emitting diode (“LED”) acting as a light source to produce the white light. In the last method, a yellow phosphor may be excited by a blue LED acting as a light source to produce the white light.
According to the method for producing white light by exciting a yellow phosphor using a blue LED as a light source, the white light is generally produced by combining the blue LED with Y3Al5O12:Ce3+, Tb3Al5O12:Ce3+, (Sr,Ba)2SiO4:Eu2+, or the like as the yellow phosphor. In particular, Y3Al5O12:Ce3+ is known as a phosphor suitable for use in a white light emitting device due to its excellent efficiency and wide emitting bands. However, the color rendering properties of the Y3Al5O12:Ce3+ phosphor are generally insufficient, and thus only cold white light may be generated using this method due to an insufficient red light emission.
To address the above deficiencies, a silicate-based phosphor has been developed to be used as an orange-yellow phosphor. A white light emitting device generating white light by exciting the silicate-based phosphor using a blue LED light source is known.